In U.S. Pat. No. 5,181,224, there is disclosed a configuration of cylindrical microlenses in which a "crossed" pair of lenses are used to collimate or focus the beam of a laser diode.
In a paper presented by the present inventor at the July 1993 Proceedings of the Society of Photo-Optical Instrumentation Engineers, entitled "CYLINDRICAL MICRO-OPTICS", there is disclosed such a pair of crossed cylindrical microlenses which are held in spaced relation to each other by a spacer in which the lenses are mounted. Such a spacer is used to attach a pair of microlenses to a laser diode during or after the assembly of the diode form a semiconductor chip, heatsink, and housing.
In U.S. patent application Ser. No. 08/725,151 entitled: "ELECTRO-OPTICAL DEVICE WITH INTEGRAL LENS", there is disclosed a scheme for mounting a long cylindrical microlens to a row of laser diode chips which has been cleaved from a wafer. First, the lens and the diode row are positioned on a substrate. The long lens is then aligned to the diode row by turning on one of the diodes and actively aligning the lens by inspection of the laser beam. The lens and diode are at this point fixed to the substrate to establish their relative position. Then the Lens/diode row is cut into individual diode chips.
The active alignment described in U.S. patent application Ser. No. 08/725,151 entitled: "ELECTRO-OPTICAL DEVICE WITH INTEGRAL LENS", may not be suitable for high volume production. In a U.S. patent application entitled "MULTIPLE ELEMENT LASER DIODE ASSEMBLY INCORPORATING A CYLINDRICAL MICROLENS", filed on Apr. 11, 1997 and identified by Attorney's Docket No. P718, there is described another diode/microlens system in which the microlens does not correct for astigmatism of the diode beam, which is instead corrected downstream with a larger lens or other means. In this system no active alignment is required to position the microlens adjacent to the laser diode facet, so automation of the process is possible. However, other means are then required to correct for the astigmatism of the beam.
It would be desirable to have a laser diode/microlens system in which active alignment of the beam was not required, but in which the addition of a larger lens downstream could also be avoided.